Screening with flexible sigmoidoscopy reduces the incidence of colorectal cancer by 20% and deaths from the disease by 27%, a large Norwegian population based study1 has shown. The study compared people who were undergoing screening with an unscreened control group.

Researchers used the Norwegian population register to randomly sample equal numbers of men and women aged 50 to 64 living in Oslo or the county of Telemark. They were randomly allocated to screening with either once only flexible sigmoidoscopy (n=10 283) or a combination of flexible sigmoidoscopy plus faecal occult blood testing (n=10 289), and the remaining people in those areas who were not screened became the control group (n=78 220).